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 By: drstevewu (offline)  Friday, August 18 2017 @ 03:34 AM CDT (Read 1601 times)
drstevewu

There are three classes that have an equal number of pupils. 331/3% (thirty-three and one-third percentage) of the boys in the classes are in Class A. The number of boys in Class C is equal to the number of girls in Class B. What fraction of pupils in the classes are girls? (Ans: 1/2)

Cheers,
Steve

Junior

Registered: 04/20/10
Posts: 31

 By: echeewh (offline)  Wednesday, August 30 2017 @ 10:25 PM CDT
echeewh

Hey Steve,

Following pls find my explanation and worked solution.

A : (1/3) boys
B + C : (2/3) boys

Given that the number of boys in Class C is equal to the number of girls in Class B, we have ...

C (boys) = B (girls)
C (girls) = B (boys)

Hence,
C (boys) + B (boys) can fill up one class given that each class contains equal number of pupils.

And, we also know ...

C (boys) + B (boys) --> (2/3) boys

Therefore, (2/3) boys will occupy 1 class (for e.g. B ), while the other remaining class (C) will be occupied by all girls.

In other words, the (2/3) boys can form one class; while the girls (from B and C) will form another class.

Given that (1/3) boys are in A and (2/3) boys can form 1 class,

(1/3) boys will occupy half (1/2) of class A while the other half of class A will be occupied by girls.

Since all the boys can occupy 1 1/2 classes, the remaining 1 1/2 classes will be occupied by the girls

(1 1/2) รท 3 = (1/2)

Half (1/2) of the classes are girls

=======

Trust this helps.

Do let me know again if there is further clarification.

Cheers,
Edward

Active Member

Registered: 04/21/11
Posts: 627

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